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+------------------------------------------------------------------------------
+-- --
+-- GNAT LIBRARY COMPONENTS --
+-- --
+-- ADA.CONTAINERS.GENERIC_SORT --
+-- --
+-- B o d y --
+-- --
+-- Copyright (C) 2011, Free Software Foundation, Inc. --
+-- --
+-- GNAT is free software; you can redistribute it and/or modify it under --
+-- terms of the GNU General Public License as published by the Free Soft- --
+-- ware Foundation; either version 3, or (at your option) any later ver- --
+-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
+-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
+-- or FITNESS FOR A PARTICULAR PURPOSE. --
+-- --
+-- As a special exception under Section 7 of GPL version 3, you are granted --
+-- additional permissions described in the GCC Runtime Library Exception, --
+-- version 3.1, as published by the Free Software Foundation. --
+-- --
+-- You should have received a copy of the GNU General Public License and --
+-- a copy of the GCC Runtime Library Exception along with this program; --
+-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
+-- <http://www.gnu.org/licenses/>. --
+-- --
+-- This unit was originally developed by Matthew J Heaney. --
+------------------------------------------------------------------------------
+
+-- This algorithm was adapted from GNAT.Heap_Sort (see g-heasor.ad[sb])
+
+with System;
+
+procedure Ada.Containers.Generic_Sort (First, Last : Index_Type'Base) is
+ type T is range System.Min_Int .. System.Max_Int;
+
+ function To_Index (J : T) return Index_Type;
+ pragma Inline (To_Index);
+
+ function Lt (J, K : T) return Boolean;
+ pragma Inline (Lt);
+
+ procedure Xchg (J, K : T);
+ pragma Inline (Xchg);
+
+ procedure Sift (S : T);
+
+ --------------
+ -- To_Index --
+ --------------
+
+ function To_Index (J : T) return Index_Type is
+ K : constant T'Base := Index_Type'Pos (First) + J - T'(1);
+ begin
+ return Index_Type'Val (K);
+ end To_Index;
+
+ --------
+ -- Lt --
+ --------
+
+ function Lt (J, K : T) return Boolean is
+ begin
+ return Before (To_Index (J), To_Index (K));
+ end Lt;
+
+ ----------
+ -- Xchg --
+ ----------
+
+ procedure Xchg (J, K : T) is
+ begin
+ Swap (To_Index (J), To_Index (K));
+ end Xchg;
+
+ Max : T := Index_Type'Pos (Last) - Index_Type'Pos (First) + T'(1);
+
+ ----------
+ -- Sift --
+ ----------
+
+ procedure Sift (S : T) is
+ C : T := S;
+ Son : T;
+ Father : T;
+
+ begin
+ loop
+ Son := C + C;
+
+ if Son < Max then
+ if Lt (Son, Son + 1) then
+ Son := Son + 1;
+ end if;
+ elsif Son > Max then
+ exit;
+ end if;
+
+ Xchg (Son, C);
+ C := Son;
+ end loop;
+
+ while C /= S loop
+ Father := C / 2;
+
+ if Lt (Father, C) then
+ Xchg (Father, C);
+ C := Father;
+ else
+ exit;
+ end if;
+ end loop;
+ end Sift;
+
+-- Start of processing for Generic_Sort
+
+begin
+ for J in reverse 1 .. Max / 2 loop
+ Sift (J);
+ end loop;
+
+ while Max > 1 loop
+ Xchg (1, Max);
+ Max := Max - 1;
+ Sift (1);
+ end loop;
+end Ada.Containers.Generic_Sort;